128 
PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 
being of the forest to such small numbers as to require several years 
at least before it would be possible for such conditions to recur. 
The investigations having been conducted in September, some time 
after the death of all of the caterpillars and pupae, it was no longer 
possible to determine with assurance the cause for the peculiar condi- 
tions, but everything conspired to indicate .that nothing less than an 
epidemic of disease had been responsible. The condition* of the 
pupal shells which hung upon the trees in countless thousands was in 
every respect identical with the condition of the pupal shells which 
are to be found in Massachusetts in every locality where the disease 
has prevailed to a destructive extent the season before. Among the 
old egg masses which plastered the extreme base of nearly every tree 
in most of the localities visited were found a variable, and sometimes 
a very large, proportion which had hatched only in part or not at all. 
The appearance of these unhatched masses was identical in every 
respect with the appearance of similarly large numbers which are 
frequently found in Massachusetts. The reason for the nonhatching 
of the eggs is not yet plain, but it is the consensus of opinion that this 
is probably associated with the "wilt" disease. It is known that 
affected caterpillars may pupate before death, and it seems not illogi- 
cal to suppose that slightly affected caterpillars may pupate and 
produce moths which are able to deposit their eggs, but that these 
eggs fail to hatch as the direct result of the taint in the blood of 
their parent. 
These Russian experiences seem, on the whole, to indicate that 
in that country the gipsy moth is not controlled by its parasites to 
an extent which serves to remove it from the ranks of a destructive 
pest. But as one day after another in the field at Kharkof served 
more and more indelibly to deepen this conviction, it served equally, 
first to create, and finally in retrospect to confirm, the observer in 
another, which was, in effect, that if this was the best that could be 
expected of disease as a factor in the control of the gipsy moth in its 
native home then something better than disease must be found to 
control it in America. Just so long as conditions similar to those seen 
in Kharkof or pictured in the letters of Prof. Kincaid are allowed to 
prevail in Massachusetts just so long will the incentive remain to see 
the parasite-introduction experiment carried on until success is either 
achieved or proved impossible. Conditions similar to those prevail- 
ing in Russia emphatically do not prevail in western Europe, nor, 
according to all accounts, in Japan. Natural conditions in western 
Europe and in Japan are in many respects more like those of our own 
Eastern States than are those of Kharkof Province. Conditions in 
Kief Province, even, are much more like those of Massachusetts than 
are those of Kharkof, and in Kief parasite control seemed to be an 
